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INR: Liver Function Test

for Veterans and the Public

INR (international normalized ratio)

International normalized ratio (INR) is blood-clotting test. It is a test used to measure how quickly your blood forms a clot, compared with normal clotting time.

Explanation of test results:

A normal INR is 1.0. Each increase of 0.1 means the blood is slightly thinner (it takes longer to clot). INR is related to the prothrombin time (PT). If there is serious liver disease and cirrhosis, the liver may not produce the normal amount of proteins and then the blood is not able to clot normally. When your doctor is evaluating the function of your liver, a high INR usually means that the liver is not working as well as it could because it is not making the blood clot normally.

Other things to know:

  • Some patients take a drug called Coumadin (warfarin), which elevates the INR, for the purpose of "thinning" the blood.
  • The INR is another way of measuring the blood-clotting time and it is easier to determine than the PT.